Plain paper and paperboard are not used to protect food for long periods of time due to their poor barrier properties and leaching of impurities into the food products. If paper/cartons are to be used in direct contact with food they need to be coated with a range of materials. Multi-layer packaging materials (typically 3 to 9 layers) enhance the functional and protective properties of the packaging. Coating application techniques are well known, the most common ones are; spraying, blade and rotating (or printing).
Examples of materials which have been used for these coatings include wax, perfluorooctanoic acid, various high barrier polymers and polyvinylidene chloride. However, most of these materials are not recyclable, biodegradable or compostable, while some present health risks if combusted.